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TOMOYO Linux Cross Reference
Linux/kernel/power/process.c

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  1 /*
  2  * drivers/power/process.c - Functions for starting/stopping processes on 
  3  *                           suspend transitions.
  4  *
  5  * Originally from swsusp.
  6  */
  7 
  8 
  9 #undef DEBUG
 10 
 11 #include <linux/interrupt.h>
 12 #include <linux/oom.h>
 13 #include <linux/suspend.h>
 14 #include <linux/module.h>
 15 #include <linux/sched/debug.h>
 16 #include <linux/sched/task.h>
 17 #include <linux/syscalls.h>
 18 #include <linux/freezer.h>
 19 #include <linux/delay.h>
 20 #include <linux/workqueue.h>
 21 #include <linux/kmod.h>
 22 #include <trace/events/power.h>
 23 
 24 /* 
 25  * Timeout for stopping processes
 26  */
 27 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
 28 
 29 static int try_to_freeze_tasks(bool user_only)
 30 {
 31         struct task_struct *g, *p;
 32         unsigned long end_time;
 33         unsigned int todo;
 34         bool wq_busy = false;
 35         ktime_t start, end, elapsed;
 36         unsigned int elapsed_msecs;
 37         bool wakeup = false;
 38         int sleep_usecs = USEC_PER_MSEC;
 39 
 40         start = ktime_get_boottime();
 41 
 42         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
 43 
 44         if (!user_only)
 45                 freeze_workqueues_begin();
 46 
 47         while (true) {
 48                 todo = 0;
 49                 read_lock(&tasklist_lock);
 50                 for_each_process_thread(g, p) {
 51                         if (p == current || !freeze_task(p))
 52                                 continue;
 53 
 54                         if (!freezer_should_skip(p))
 55                                 todo++;
 56                 }
 57                 read_unlock(&tasklist_lock);
 58 
 59                 if (!user_only) {
 60                         wq_busy = freeze_workqueues_busy();
 61                         todo += wq_busy;
 62                 }
 63 
 64                 if (!todo || time_after(jiffies, end_time))
 65                         break;
 66 
 67                 if (pm_wakeup_pending()) {
 68                         wakeup = true;
 69                         break;
 70                 }
 71 
 72                 /*
 73                  * We need to retry, but first give the freezing tasks some
 74                  * time to enter the refrigerator.  Start with an initial
 75                  * 1 ms sleep followed by exponential backoff until 8 ms.
 76                  */
 77                 usleep_range(sleep_usecs / 2, sleep_usecs);
 78                 if (sleep_usecs < 8 * USEC_PER_MSEC)
 79                         sleep_usecs *= 2;
 80         }
 81 
 82         end = ktime_get_boottime();
 83         elapsed = ktime_sub(end, start);
 84         elapsed_msecs = ktime_to_ms(elapsed);
 85 
 86         if (todo) {
 87                 pr_cont("\n");
 88                 pr_err("Freezing of tasks %s after %d.%03d seconds "
 89                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
 90                        wakeup ? "aborted" : "failed",
 91                        elapsed_msecs / 1000, elapsed_msecs % 1000,
 92                        todo - wq_busy, wq_busy);
 93 
 94                 if (wq_busy)
 95                         show_workqueue_state();
 96 
 97                 if (!wakeup) {
 98                         read_lock(&tasklist_lock);
 99                         for_each_process_thread(g, p) {
100                                 if (p != current && !freezer_should_skip(p)
101                                     && freezing(p) && !frozen(p))
102                                         sched_show_task(p);
103                         }
104                         read_unlock(&tasklist_lock);
105                 }
106         } else {
107                 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
108                         elapsed_msecs % 1000);
109         }
110 
111         return todo ? -EBUSY : 0;
112 }
113 
114 /**
115  * freeze_processes - Signal user space processes to enter the refrigerator.
116  * The current thread will not be frozen.  The same process that calls
117  * freeze_processes must later call thaw_processes.
118  *
119  * On success, returns 0.  On failure, -errno and system is fully thawed.
120  */
121 int freeze_processes(void)
122 {
123         int error;
124 
125         error = __usermodehelper_disable(UMH_FREEZING);
126         if (error)
127                 return error;
128 
129         /* Make sure this task doesn't get frozen */
130         current->flags |= PF_SUSPEND_TASK;
131 
132         if (!pm_freezing)
133                 atomic_inc(&system_freezing_cnt);
134 
135         pm_wakeup_clear();
136         pr_info("Freezing user space processes ... ");
137         pm_freezing = true;
138         error = try_to_freeze_tasks(true);
139         if (!error) {
140                 __usermodehelper_set_disable_depth(UMH_DISABLED);
141                 pr_cont("done.");
142         }
143         pr_cont("\n");
144         BUG_ON(in_atomic());
145 
146         /*
147          * Now that the whole userspace is frozen we need to disbale
148          * the OOM killer to disallow any further interference with
149          * killable tasks. There is no guarantee oom victims will
150          * ever reach a point they go away we have to wait with a timeout.
151          */
152         if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
153                 error = -EBUSY;
154 
155         if (error)
156                 thaw_processes();
157         return error;
158 }
159 
160 /**
161  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
162  *
163  * On success, returns 0.  On failure, -errno and only the kernel threads are
164  * thawed, so as to give a chance to the caller to do additional cleanups
165  * (if any) before thawing the userspace tasks. So, it is the responsibility
166  * of the caller to thaw the userspace tasks, when the time is right.
167  */
168 int freeze_kernel_threads(void)
169 {
170         int error;
171 
172         pr_info("Freezing remaining freezable tasks ... ");
173 
174         pm_nosig_freezing = true;
175         error = try_to_freeze_tasks(false);
176         if (!error)
177                 pr_cont("done.");
178 
179         pr_cont("\n");
180         BUG_ON(in_atomic());
181 
182         if (error)
183                 thaw_kernel_threads();
184         return error;
185 }
186 
187 void thaw_processes(void)
188 {
189         struct task_struct *g, *p;
190         struct task_struct *curr = current;
191 
192         trace_suspend_resume(TPS("thaw_processes"), 0, true);
193         if (pm_freezing)
194                 atomic_dec(&system_freezing_cnt);
195         pm_freezing = false;
196         pm_nosig_freezing = false;
197 
198         oom_killer_enable();
199 
200         pr_info("Restarting tasks ... ");
201 
202         __usermodehelper_set_disable_depth(UMH_FREEZING);
203         thaw_workqueues();
204 
205         read_lock(&tasklist_lock);
206         for_each_process_thread(g, p) {
207                 /* No other threads should have PF_SUSPEND_TASK set */
208                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
209                 __thaw_task(p);
210         }
211         read_unlock(&tasklist_lock);
212 
213         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
214         curr->flags &= ~PF_SUSPEND_TASK;
215 
216         usermodehelper_enable();
217 
218         schedule();
219         pr_cont("done.\n");
220         trace_suspend_resume(TPS("thaw_processes"), 0, false);
221 }
222 
223 void thaw_kernel_threads(void)
224 {
225         struct task_struct *g, *p;
226 
227         pm_nosig_freezing = false;
228         pr_info("Restarting kernel threads ... ");
229 
230         thaw_workqueues();
231 
232         read_lock(&tasklist_lock);
233         for_each_process_thread(g, p) {
234                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
235                         __thaw_task(p);
236         }
237         read_unlock(&tasklist_lock);
238 
239         schedule();
240         pr_cont("done.\n");
241 }
242 

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